INTRODUCTION: Injectable self‐hardening and swelling hydrogel covalently linked with various peptide is a potential cell carrier for nucleus pulposus tissue engineering. Arginine‐glycine‐aspartic acid (RGD) has been incorporated into various biomaterials to promote cell adhesion and improve biological activity of the cell and which cell adhesion to the scaffold provides signals for directing cell functions and fate. RGD has shown to be involved in the mechano‐transduction of intervertebral disc cells. The aim of the study is to determine the performance of nucleus pulposus cells (NPC) and mesenchymal stem cell (MSC) embedded in poly‐ethylene‐glycol (PEG) hydrogel with and without RGD.
METHODS: Primary bovine coccygeal NPC and human bone marrow MSCs (expanded in monolayer up to passage 4, ethically approved) were embedded in a soft, degradable PEG‐hydrogel covalently linked with and without 50μM RGD (Q‐Gel inc., Switzerland) and were molded in a 4mm Ø and 3mm height disc‐like construct. Glycosaminoglycan (GAG), DNA content, cell viability and morphology were evaluated by live/dead stain and confocal microscopy. Parameters were measured after 21 days of culture in serum free medium and standard culture conditions. Gene expression of MSC was evaluated by real‐time PCR.
RESULTS: Both NPC and MSC cell viability were maintained at around 70% over the culture period. MSC are spread out in PEG‐RGD hydrogel showed cell adhesion to the hydrogel and forming a cell network in the PEG‐RGD gel. MSC maintained their typical fibroblast‐like shape if cultured with RGD, without RGD the MSC were rounded and lacked filopodia. NPC were spread out and arose dendrites‐like morphology in the RGD‐PEG gel and their round morphology was maintained in PEG gel without RGD.
DISCUSSION: The hydrogel lacking RGD preserved the "NP" phenotype whereas undifferentiated MSCs preserve their fibroblast‐like phenotype in the RGD‐gel. These synthetic hydrogels are potentially interesting for nucleus pulposus tissue engineering use.